Clean Water


No choice but dirty water

Most people in the Zaka region of Zimbabwe have no choice about what they will drink. The only available water sources are almost always heavily contaminated and few people have access to water treatment.


Clean water boosts health

Children can stay in school and learn and adults can work and care for their families. It’s estimated that every $1 invested in water and sanitation produces an economic return of $4 by keeping people healthy and productive.

biosand water filters (BSF)

biosand water filters

A single BSF can purify enough water to supply the needs of a household of up to 10 people. All of our water filters are made locally in Zaka, providing the dignity of employment to eight people and a source of economic activity for the local area.

While there are many water purification methods, nearly all of them rely on a source of power, complex manufacturing processes, frequent maintenance or replacement, or a continuous supply of chemicals.  Biosand filters (BSF) have none of these requirements, instead they:

  • have no moving parts, mechanical or electrical components
  • require no fuel or electricity
  • are significantly less expensive than other options
  • require very simple maintenance
  • are constructed from materials available in almost every community
  • are virtually indestructible and too heavy to steal

For these reasons, BSFs are extremely well-suited to purify water in rural regions of the developing world.

How they work

Made from concrete, sand, and gravel, BSFs consist of a chimney-like container about 1 meter tall with a 20 cm square opening. The container is filled with several centimetres of coarse and fine gravel followed by carefully prepared fine sand. When the filter is filled with water the sand and gravel layers are fully submerged.  In two to four weeks, a layer of microorganisms (the ‘biological layer’) grows on the surface.  At this point the filter is ready for use.

BSFs purify contaminated water by several mechanisms. When dirty water from a contaminated stream or well is poured into the BSF:

  • dirt and larger particles are trapped at the top of the sand layer
  • the biological layer ‘eats’ a significant portion of the parasites and other microorganisms within the water
  • fine sand traps remaining bacteria where they suffocate due to lack of oxygen.

Gravity then pulls the purified water to the gravel layer at the bottom and up a standpipe to a spigot.  Water that exits the filter is clear, clean and safe (and even cool!).

While sand has been used for centuries to purify water, the sand preparation method and active biological layer of BSFs are uniquely effective at filtering heavily contaminated water. The process removes virtually all parasites and almost all bacteria and viruses. Because filters must be made locally, they offer other benefits to the community such as employment opportunities, business growth for local suppliers who can provide raw materials for the filters as well as providing a source of community pride.


Community Wells

Drilling a well is a significant and costly project, but the impact on a community is profoundly life-changing. This single intervention can be enough to move families from chronic illness to health and productivity. When properly maintained, wells provide an entire community access to a clean source of water.

Prior to installing a well, local people are not only trained on how to repair the well, but are trained in a savings program known as table banking to provide the funds to make those repairs. This approach ensures that the funds invested in wells provide vulnerable communities with a long-term sustainable water solution.